1. Field of the Invention
The invention relates to a device for electromechanical stimulation and testing of hearing, comprising an electromechanical transducer for producing mechanical vibrations, a mechanical coupling element for transmitting mechanical stimulation vibrations from the electromechanical transducer without surgery through the external auditory canal to the umbo and thus to the manubrium mallei of the ossicular chain, positioning means for positioning the coupling element with reference to the umbo, and fixing means for secure, play-free linkage of the positioning means to the human body, especially the human skull.
2. Description of Related Art
A device for electromechanical stimulation and testing of hearing is known from U.S. Pat. No. 5,833,626. A positioning means suitable for this purpose is detailed in U.S. Pat. No. 5,776,144. Such a device makes it possible to demonstrate pre-operatively in a noninvasive manner, i.e., without surgery, to the test subject awaiting implantation the improvement of hearing and sound quality. This improvement can be expected by the use of a partially or fully implantable hearing system which stimulates the middle or inner ear with mechanical vibrations by being coupled to an electromechanical transducer. A fully implantable hearing system of this type is described, among others, in the paper of H. Leysieffer, et al., xe2x80x9cA totally implantable hearing device for the treatment of sensorineural hearing loss: TICA LZ 3001,xe2x80x9d HNO, vol. 46, October 1998, pages 853 to 863.
The positioning means makes it possible to precisely route to the destination the acting end of the mechanical coupling element, for example a coupling rod which is connected to the electromechanical transducer. A fixing means fixes the spatial position between the positioned coupling element and the umbo. Practical experience has shown that a certain risk exists in using the device. The positioning and/or fixing means may be accidentally touched and moved. The tympanic membrane or the ossicular chain can be damaged, or pressure can be exerted on the inner ear and the semicircular ducts. This can lead to vertigo or even hearing loss. This risk also exists for spontaneous head movements of the test subject.
A primary object of the present invention is to further increase the safety of a device of the initially mentioned type.
According to the invention, this and other objects are achieved by a device such that, between the positioning means and the electromechanical transducer there is an intermediate element which is designed and dimensioned such that it transmits quasisteady-state positioning adjustments from the positioning means to the electromechanical transducer, but reduces transmission of at least dynamic forces from the positioning means to the coupling element at least to such an extent that the risk of middle or inner ear damage is substantially reduced.
In the stimulation and testing device of the invention, the transducer together with the coupling element follows the relatively slow position changes which are called quasisteady-state here and which are caused by the actuation of the positioning means. The physician can thus guide the active end of the coupling element precisely and free of relative movements to structures in the human body, especially to the umbo, as the target point. Conversely, in the case of an unintentional external action which generally takes place by jerks and jolts, for example by hitting the positioning means with the hand, an instrument or the like, the dynamic forces acting on the positioning means are kept away from the transducer and the coupling element at least to a substantial extent.
The intermediate element may be made as a spring member, which is a structurally simple approach. Here, the spring member, electromechanical transducer and coupling element from a spring/mass system which preferably has a natural frequency in the range from 0.5 to 5 Hz.
The spring member can consist of one or more flexional springs. The springs may be simple flexional springs.
Preferably, the coupling element is made as a coupling rod, and the spring member is aligned at least roughly perpendicular to the longitudinal axis of the coupling rod.
These and further objects, features and advantages of the present invention will become apparent from the following description when taken in connection with the accompanying drawing which, for purposes of illustration only, shows a single embodiment in accordance with the present invention.